In both images, the eruption's extent is clear, as volcanic emissions block the view of most of the island. The brown or tan plume in the east is volcanic ash. The bright ''cloud'' to the immediate left of the brown ash resembles a regular cloud but likely results from the volcano itself. If a volcanic ash plume reaches a high enough altitude, the water content of that plume turns to ice crystals, and these ice crystals ''white out'' the ash content that would otherwise appear tan or brown. According to Simon Carn of the www.jcet.umbc.edu/ Joint Center for Earth Systems Technology, Rabaul produced a similar ice-rich cloud in a major eruption in 1994.
The false-color image provides a somewhat better contrast between the ice-rich plume produced by the volcano and the nearby clouds. In the false-color image, the plume is a slightly deeper shade of blue-green.
www.volcano.si.edu/world/volcano.cfm?vnum=0502-14= Rabaul is a en.wikipedia.org/wiki/Shield_volcano shield volcano formed from deposits left by earlier eruptions. It has produced major explosions during historical times, including large eruptions in 1878 and 1994. The 1994 eruption produced simultaneous activity from the Vulcan and Tavurvur Volcanoes.
NASA image created by Jesse Allen, Earth Observatory, using data provided courtesy of the rapidfire.sci.gsfc.nasa.gov/ MODIS Rapid Response team.